In a push-button switch utilized for a power window, door mirror or the like, high current of 100 to 500 mA is conducted, so that a plate-shaped metal member is used as a member for the push-button switch (which may be merely called hereinafter a push-button switch member). Further, during a normally-closed type contact, in order to prevent a so-called sticking phenomenon in which a push-button switch member is closely contacted by an opposing electrode and is never separated therefrom, a plate-shaped metal member is used as the push-button switch member.
FIG. 7 is a schematic partial sectional view showing a push-button switch capable of withstanding such a high current.
In this figure, reference numeral 1 denotes a contact structure composed of a plate-shaped metal, a keypad 2 is formed of a resin such as silicone rubber which is operatively pushed from an external side, and the contact structure 1 is integrally formed on the keypad 2 in a manner opposing an opposing electrode 4 of a stationary substrate 3 so as to be capable of being contacted by the contact structure 1, thus constituting a movable contact.
In a conventional technology, there has been widely used a metal plate, which is formed by gold-plating a German silver metal sheet, and then punching out therefrom a predetermined shape. At a time when such contact structure 1 is contacted with the opposing electrode 4, since a current passes through such contacting of the metal plate having good conductive performance with the opposing electrode 4, high current can be conducted, and moreover, since the metal plate has a strength strong enough to substantially prevent the contact structure 1 from being damaged or broken through a repeated pushing or pressing operation 5 applied to a push-button B, and hence, strong enough to provide desired durability.
However, in the contact structure 1 composed of such plate-shaped metal, the metal plate is too strong to be deformed. Accordingly, as shown in FIG. 8, if fine foreign material 5 such as dirt or dust having an insulating property intrudes into the switch and adheres to a portion between the contact structure 1 and the opposing electrode 4, it is difficult for the metal plate to be deformed in accordance with a shape of the fine foreign material 5 at a time when the contact structure 1 contacts the opposing electrode 4, which will adversely result in formation of a wide gap 5a therebetween, largely reducing a contacting area and, hence, causing defective conduction of the push-button switch, thus providing problems.